HCG questions (first baby and nervous)

I am only 4 weeks a long. On Thursday last week, my HCG was at 48. On Saturday, it was 123 however today, it only went up to 173. Should I be concerned? I haven’t had any bleeding since last week on Wednesday, only very light intermittent cramping, and just today but breast’s are super sore.

I thought it was supposed to double every 48 hours or something around there. I feel like it’s really low and not progressing appropriately. They’re drawing my blood again Thursday to see how it goes.

Anyone else have experiences with this?